s390: Add a mechanism to get the subchannel id.

This will be needed by the new virtio-ccw transport.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/ccwdev.h b/arch/s390/include/asm/ccwdev.h
index 1cb4bb3..9ad79f7 100644
--- a/arch/s390/include/asm/ccwdev.h
+++ b/arch/s390/include/asm/ccwdev.h
@@ -18,6 +18,9 @@
 struct ccw1;
 struct ccw_dev_id;
 
+/* from asm/schid.h */
+struct subchannel_id;
+
 /* simplified initializers for struct ccw_device:
  * CCW_DEVICE and CCW_DEVICE_DEVTYPE initialize one
  * entry in your MODULE_DEVICE_TABLE and set the match_flag correctly */
@@ -226,5 +229,7 @@
 // FIXME: these have to go
 extern int _ccw_device_get_subchannel_number(struct ccw_device *);
 
+extern void ccw_device_get_schid(struct ccw_device *, struct subchannel_id *);
+
 extern void *ccw_device_get_chp_desc(struct ccw_device *, int);
 #endif /* _S390_CCWDEV_H_ */